ShanerRS

So I’ve been having this issue for some time now.. it’s a 91 RS with a 305 tbi. All the other cylinders are firing the way they should but number 1 has a weak/low spark to where I can still touch the header and hear the miss. I’ve changed the hole distributor, plugs and wires. The problem happened before all that and it still persists.
I’ve been trying to time it but the probe gun won’t flash on that wire bc of the weakness.. I’ve checked all others and they all had a flash

RBob

iTrader: (1)

It may be a flat intake lobe on the cam. A compression check on that cylinder will show it. Could also pull the valve cover and check that the intake rocker arm is active.

With little to no compression the plug will fire at a very low voltage, which is likely why the timing light won't trigger.

RBob.

ShanerRS

I’ve recently swapped the cam out to a lt4 hot cam. The problems happened before I did the swap. I’ve checked all the rocker arms as I run the engine and they all are in order. Just seems like I’m getting weak spark to all cylinders mostly number 1. I don’t have access to a scan tool at the moment for anything. But would the esc box have something to do with it??

RBob

iTrader: (1)

Only item in the secondary ignition system that you didn't change is the coil. Could be a bad ignition coil.

Likely not the ESC module, if it was that would just cause the ECM to retard the spark timing. Which would cause low power.

RBob.

Schurkey

Sorry.

Schurkey

Any cause of low voltage to one cylinder produces that sort of misfire with those diagnostic hints.

Possible. A failed coil would likely have symptoms of misfire on more than one cylinder.

First Guess: Fouled spark plug. The potential for voltage is there, but it's bleeding off through a conductive glaze or petroleum film on the porcelain. Remove plug, test compression. Clean plug via grit-blasting, or replace plug. Conductive glaze can be nearly invisible, so don't go by how the plug "looks". Of course, if it's visibly fouled...

True Story: I bought a K2500 7.4L to plow snow with just before New Years last year. Ran like ****, misfire counts were out-of-sight high for #8. Trans had no lockup for the torque converter. Bought it, drove it home. Pulled #8 spark plug. I knew what was wrong before I even got the plug fully unscrewed--I could feel the crack in the porcelain with my fingertips. Did a compression test which came out "OK". Put a used but not broken spark plug into #8. Misfires ended, and I discovered that the TCC won't engage if the computer senses misfire--so a used spark plug fixed both the engine AND the transmission.

ShanerRS

I’ve had this problem since before I pulled the engine and did the cam and gaskets.. I’ll buy new plugs and put them in and it’ll run like a raped ape for a few days and then I’ll got to start it one day and number one won’t be firing.. I’ve changed every sensor, and the coil. Even the ecm. Maybe the accel coil I put in took a **** and I’ll try plugging in the stock one and see if that changes anything after I put some new plugs in it